The present invention relates in general to a strobe tuner for indicating whether a musical instrument is tuned correctly.
Strobe tuners are employed to sense the pitch of a note being played by a musical instrument and indicate whether the note is in tune with a reference standard. A first type of strobe tuner employs a single strobe disc which is rotated by a synchronous motor at a precise speed determined by the reference standard and vernier pitch offset to which the musical instrument is to be tuned. An audio circuit is employed to detect the note being played by the instrument, and generate an oscillating electrical signal whose frequency is directly proportional to the note's frequency. This oscillating signal causes a light source positioned behind the strobe disc to flash at frequencies that are components of the sound generated by the musical instrument. If the instrument is in tune with the reference standard, the light source will flash in synchronism with a spinning pattern of black rectangles on the strobe disc, and thus produce a pattern that appears to be stationary. If the instrument's tone is flat relative to the reference standard, the strobe disc pattern will appear to be rotating counterclockwise at a speed proportional to the error in frequency. On the other hand, if the instrument's tone is sharp relative to the standard, the strobe disc pattern will appear to be rotating clockwise.
Single disc strobe tuners typically have some type of switching means or the like for selecting one note at a time to which the instrument is to be tuned so that the speed of the synchronous motor can be changed for each note as necessary. Another type of strobe tuner for tuning an instrument to multiple notes employs multiple strobe discs, one for each of the notes to which the instrument is to be tuned. For example, 12 wheel strobe tuners are known wherein strobe discs for each of the 12 natural and sharp notes in an octave are provided. These devices employ a single motor to drive all 12 strobe discs through a gear train. As a result, the speed relationships between the strobe discs are fixed by the gear ratios to an equal-tempered relationship. In particular, each note is related to an adjacent note by a factor of approximately the 12th root of 2.
A notable drawback to previous strobe tuners is that they cannot be readily adapted for use with complex tuning arrangements, such as unequal temperaments or stretch tuning. In unequal temperaments, the notes in each octave are not separated equally from one another. Stretch tuning is a technique employed for tuning string or bar percussion instruments, such as pianos, wherein notes played from keys one octave apart are tuned slightly farther apart than the exact ratio of 2:1. This is desired by many instrument tuners as a means to compensate for mechanical limitations and imperfect vibrational modes in these instruments. Obviously, neither unequal temperaments nor stretch tuning can be accommodated by the previous 12 disc strobe tuner since the gear ratios of the disc drive train prevent independent adjustment of the speed of one disc relative to the other discs. Even with previous single disc strobe tuners it is very difficult to accommodate unequal temperaments and stretch tuning since such schemes typically require adjustment in a very precise range of a fraction of a semitone. This would require some type of fine vernier adjustment for the strobe disc which would have to be manually adjusted for each note in the scale. A still further drawback to previous 12 disc strobe tuners is that their gear trains inherently tend to generate a lot of noise. This noise can interfere with the operation of the strobe tuner which ideally should be used in as quiet an environment as possible to isolate its sensitivity to the sounds played by the instrument to be tuned.